1. Field
The system and method of the present invention pertains to the field of recycling waste materials comprising cellulosic fiber and thermoplastic resin; more particularly, an improved method for processing recycled such combustible materials into products capable of generating high heat outputs.
2. Background
An increasing number of consumer products are made from thermoplastic resin such as, for example, adhesive liners and medical gowns. Some products, such as, for example, disposable diapers, are primarily made up of thermoplastic resin and cellulosic fiber wherein the thermoplastic material provides a moisture-proof lining on the outside of the diaper and the cellulosic fiber provides the bulky absorbent media on the inside. The cellulosic fiber holds and retains all moisture, while the thermoplastic material ensures that there is no external leakage.
When products such diapers, adhesive liners, hygiene pads and the like are manufactured, a certain amount of waste is inevitable, resulting in so-called “pre-consumer waste.” In addition, many of these products are disposable in nature and, as a result, are used just once and thrown away resulting in “post-consumer waste.” The ultimate disposal of pre-consumer and post-consumer waste typically involves transporting it to the local landfill. Environmentalists abhor this type of disposal as being wasteful both in the manufacture and disposal of these products. For example, the manufacture of disposable diapers requires forest products to obtain the necessary cellulose and the disposal of the diapers utilizes valuable landfill space. Moreover, the U.S. Environmental Protection Agency (EPA) has placed increase restrictions on landfill requirements. For example, the EPA has recently enforced the requirement of double lining landfills for disposal of paper mill sludge. Consequently, there has been a dramatic increase in cost for establishing new landfills that comply with EPA requirements for paper mill by-products.
In addition to the increased reluctance to use forest products and increased restrictions in landfill requirements, there has also be an increase in demand for new sources of energy. Combustible products made from cellulosic fibers and thermoplastic resins offer a higher BTU output and provide a clean-burning alternative to conventional fuels. However, use of available cellulosic waste as a fuel source has achieved only limited acceptance to date. One reason for this is the relatively low heating value of cellulose as compared to, for example, coal. For example, cellulosic fibers alone can have a heating value of less than 7,000 BTU's per pound, while coal generally has heating value in excess of 9,000 BTU's per pound.
Methods and systems for processing materials consisting substantially of thermoplastic resin and cellulosic fiber into combustible materials are well known in the art. However, there are a number of difficulties in processing these materials. For example, in recent years, many companies have made significant advances in improving the tear-resistant properties of thermoplastic materials such as, for example, through highly cross-linking or otherwise processing the thermoplastic polymers. These highly tear-resistant materials, by their very nature, are exceptionally difficult to process using conventional means. For example, if these materials are processed through normal shredder devices, the shredder will quickly become bound-up and, in many cases, cease operating. Moreover, because the materials are combustible by nature, they have a propensity for catching fire if exposed to high heat or friction, such as during processing. As a result, if the operator is successful in maintaining the operation of the shredder, the friction involved in processing these materials creates an extreme fire hazard. There is a need, therefore, for an improved method for processing recycled combustible materials into products capable of generating high heat outputs.
As previously mentioned, a number of combustible products, and processes for manufacturing combustible products, have been patented in the United States. For example, U.S. Pat. No. 4,236,897 to Johnston discloses a fuel pellet comprised of natural cellulosic material and synthetic polymeric thermoplastic material. The patent disclosed the composition of the cellulose (substantially 5 mesh with a moisture content of about 5 to about 15 percent by weight, and comprising from about 90 to 99 percent by weight of the fuel pellet) and the thermoplastic material (between 5 and 10 mesh and comprising about 1 to 10 percent by weight of the fuel pellet). An average fuel analysis of the fuel pellets tested produced up to 9,180 BTU per pound. However, Johnson does not disclose the method for processing feedstock that maintains a continuous flow of feedstock while reducing the risk of fire.
Similarly, U.S. Pat. No. 5,342,418 to Jesse discloses a method of making a fuel pellet comprised of cellulosic material. The fuel pellet described therein is comprised of 60 to 90 percent by weight of cellulosic material, and 10 to 40 percent by weight of a thermoplastic resin. The heat output of the fuel pellets is between 9,500 and 11,500 BTU per pound. Again, the process described by Jesse does not provide for the continuous processing of feedstock while reducing the risk of fire.
Accordingly, it is an object of this invention to provide an improved method for processing recycled combustible materials consisting substantially of thermoplastic resins and cellulosic materials into products capable of generating high heat outputs such as, for example, in excess of 10,000 BTU per pound.
Another object is to provide an improved method for producing combustible products from conventional disposable diaper stock, disposable hygiene pad stock or a combination thereof.
A further object is to provide an improved method for producing combustible products from a cellulosic fiber component and a thermoplastic resin component.